Some ceremonies, such as weddings, baptisms, confirmations, and funerals, are held in a church or other house of worship, but generally one hopes that they wouldn't be too sermon-y. Other types of ceremonies, such as coffee and tea ceremonies, flag ceremonies, graduation ceremonies, the changing of the guard at Buckingham Palace, and the opening of the Olympic games (to name but a few), are largely, if not entirely, secular. There were 16 cases of Cermonies, seven of Cermony, and five of Cermonial in OhioLINK today. You all know the drill, so I'm not going to sermonize here. Just go forth and check your records, dropping that second E in there if needed.
(Chinese tea ceremony, 2010, from Wikimedia Commons.)